As of this writing, the price of ethereum classic (ETC) rocketed 20 percent to top $7.38 per coin. ETC has been on a sizzling rally for the past week.

Ethereum classic rockets 20 percent

The ETC price popped more than 20% on Thursday. | Source: TradingView

In fact, ETC is the best-performing cryptocurrency today among the top 100 largest cryptocurrencies by market cap. With today's surge, ethereum classic is easily outpacing the bitcoin price, which is moving sideways after plunging earlier in the week.

Atlantis, Istanbul Hard Forks Loom

ETC's Atlantis hard fork is less than one month away. | Source: Shutterstock

It's unclear what exactly is triggering ethereum classic's abrupt surge. However, such sudden price movements often occur ahead of hard forks - even when they're not contentious. ETC's Atlantis hard fork is now less than one month away.

While far more modest than ETC, ethereum's 3% climb to $192.70 outpaces bitcoin's recovery by a significant margin. ETH was up as high as $195.11 this afternoon.

ETH is also outpacing bitcoin today. | Source: TradingView

The ETH network's upcoming hard fork upgrade, Istanbul, is set to occur in October. It will involve six codebase modifications (also known as Ethereum Improvement Proposals, or EIP).

The Istanbul Hard Fork will be rolled out in two different phases, according to a Reddit thread. Phase 1 is tentatively scheduled for October, while Phase 2 will occur sometime in the first quarter of 2020.